1. Field of the Invention
The present invention relates to methods of producing an optical device, optical devices, optical systems, and imaging devices.
2. Description of the Related Art
In optical instruments such as cameras, an optical diaphragm and a neutral density (ND) filter are used in order to control the amount of light that enters a lens. Cellular phones and mobile terminals also are equipped with a camera, and such a camera uses an optical diaphragm (for example, Japanese Laid-Open Patent Application No. 11-231209). FIG. 1 illustrates a typical optical diaphragm. A diaphragm 910 is formed of a light blocking material to have a plate shape with an opening 911 being formed in the center. The diaphragm 910 blocks light except for the light passing through the center opening 911. In FIG. 1, the upper drawing is a plan view of the diaphragm 910, and the lower drawing illustrates a light transmittance distribution along one-dot chain line 1A-1B of the upper drawing. Recently, cellular phones and mobile terminals have been reduced in size and thickness, so that cameras as well have been reduced in size. Therefore, optical diaphragms used in cameras also have been reduced in size. When the diaphragm 910 is reduced in size, however, the diffraction of light occurs to a non-negligible extent around the opening 911, so that it is difficult to improve resolution. That is, while the number of pixels of cameras is increasing, there has been a demand for smaller optical diaphragms that do not lower resolution.
Reference may also be made to Japanese Laid-Open Patent Application No. 2011-221120 and Japanese Patent No. 4428961 for related art.